Fail with Gradle bootBuildImage and war packaging

Prior to this commit, running the bootBuildImage Gradle task on a
project configured for war packaging would result in a jar file being
built and used in the image instead of the war file. With this commit
an error will be thrown from the plugin in this case.

Fixes gh-24521

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/asciidoc/packaging-oci-image.adoc

@@ -1,6 +1,6 @@
 [[build-image]]
 == Packaging OCI Images
-The plugin can create an https://github.com/opencontainers/image-spec[OCI image] from executable jars using https://buildpacks.io[Cloud Native Buildpacks] (CNB).
+The plugin can create an https://github.com/opencontainers/image-spec[OCI image] from an executable jar file using https://buildpacks.io[Cloud Native Buildpacks] (CNB).
 Images can be built using the `bootBuildImage` task.
 
 NOTE: For security reasons, images build and run as non-root users.
@@ -8,6 +8,8 @@ See the {buildpacks-reference}/reference/spec/platform-api/#users[CNB specificat
 
 The task is automatically created when the `java` plugin is applied and is an instance of {boot-build-image-javadoc}[`BootBuildImage`].
 
+NOTE: The `bootBuildImage` task is not supported with projects using <<packaging-executable-wars, war packaging>>.
+
 NOTE: The `bootBuildImage` task can not be used with a <<packaging-executable-configuring-launch-script, fully executable Spring Boot archive>> that includes a launch script.
 Disable launch script configuration in the `bootJar` task when building a jar file that is intended to be used with `bootBuildImage`.
 

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/WarPluginAction.java

@@ -22,11 +22,13 @@ import org.gradle.api.Project;
 import org.gradle.api.artifacts.Configuration;
 import org.gradle.api.artifacts.ConfigurationContainer;
 import org.gradle.api.file.FileCollection;
+import org.gradle.api.file.RegularFile;
 import org.gradle.api.internal.artifacts.dsl.LazyPublishArtifact;
 import org.gradle.api.plugins.BasePlugin;
 import org.gradle.api.plugins.WarPlugin;
 import org.gradle.api.tasks.TaskProvider;
 
+import org.springframework.boot.gradle.tasks.bundling.BootBuildImage;
 import org.springframework.boot.gradle.tasks.bundling.BootWar;
 
 /**
@@ -51,6 +53,7 @@ class WarPluginAction implements PluginApplicationAction {
 	@Override
 	public void execute(Project project) {
 		disableWarTask(project);
+		disableBootBuildImageTask(project);
 		TaskProvider<BootWar> bootWar = configureBootWarTask(project);
 		configureArtifactPublication(bootWar);
 	}
@@ -59,6 +62,11 @@ class WarPluginAction implements PluginApplicationAction {
 		project.getTasks().named(WarPlugin.WAR_TASK_NAME).configure((war) -> war.setEnabled(false));
 	}
 
+	private void disableBootBuildImageTask(Project project) {
+		project.getTasks().named(SpringBootPlugin.BOOT_BUILD_IMAGE_TASK_NAME, BootBuildImage.class)
+				.configure((buildImage) -> buildImage.getJar().set((RegularFile) null));
+	}
+
 	private TaskProvider<BootWar> configureBootWarTask(Project project) {
 		return project.getTasks().register(SpringBootPlugin.BOOT_WAR_TASK_NAME, BootWar.class, (bootWar) -> {
 			bootWar.setGroup(BasePlugin.BUILD_GROUP);

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/BootBuildImage.java

@@ -21,6 +21,7 @@ import java.util.HashMap;
 import java.util.Map;
 
 import org.gradle.api.DefaultTask;
+import org.gradle.api.GradleException;
 import org.gradle.api.JavaVersion;
 import org.gradle.api.Project;
 import org.gradle.api.Task;
@@ -79,6 +80,7 @@ public class BootBuildImage extends DefaultTask {
 	 * @return the jar property
 	 */
 	@Input
+	@Optional
 	public RegularFileProperty getJar() {
 		return this.jar;
 	}
@@ -226,6 +228,9 @@ public class BootBuildImage extends DefaultTask {
 
 	@TaskAction
 	void buildImage() throws DockerEngineException, IOException {
+		if (!this.jar.isPresent()) {
+			throw new GradleException("Executable jar file required for building image");
+		}
 		Builder builder = new Builder();
 		BuildRequest request = createRequest();
 		builder.build(request);

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/tasks/bundling/BootBuildImageIntegrationTests.java

@@ -153,6 +153,36 @@ class BootBuildImageIntegrationTests {
 				.containsPattern("example/Invalid-Image-Name");
 	}
 
+	@TestTemplate
+	void failsWithWarPackaging() {
+		writeMainClass();
+		writeLongNameResource();
+		BuildResult result = this.gradleBuild.buildAndFail("bootBuildImage", "-PapplyWarPlugin");
+		assertThat(result.task(":bootBuildImage").getOutcome()).isEqualTo(TaskOutcome.FAILED);
+		assertThat(result.getOutput()).contains("Executable jar file required for building image");
+	}
+
+	@TestTemplate
+	void buildsImageWithWarPackagingAndJarConfiguration() throws IOException {
+		writeMainClass();
+		writeLongNameResource();
+		BuildResult result = this.gradleBuild.build("bootBuildImage");
+		String projectName = this.gradleBuild.getProjectDir().getName();
+		assertThat(result.task(":bootBuildImage").getOutcome()).isEqualTo(TaskOutcome.SUCCESS);
+		assertThat(result.getOutput()).contains("docker.io/library/" + projectName);
+		assertThat(result.getOutput()).contains("paketo-buildpacks/builder");
+		File buildLibs = new File(this.gradleBuild.getProjectDir(), "build/libs");
+		assertThat(buildLibs.listFiles())
+				.containsExactly(new File(buildLibs, this.gradleBuild.getProjectDir().getName() + ".war"));
+		ImageReference imageReference = ImageReference.of(ImageName.of(projectName));
+		try (GenericContainer<?> container = new GenericContainer<>(imageReference.toString())) {
+			container.waitingFor(Wait.forLogMessage("Launched\\n", 1)).start();
+		}
+		finally {
+			new DockerApi().image().remove(imageReference, false);
+		}
+	}
+
 	private void writeMainClass() {
 		File examplePackage = new File(this.gradleBuild.getProjectDir(), "src/main/java/example");
 		examplePackage.mkdirs();

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/tasks/bundling/BootBuildImageIntegrationTests-buildsImageWithWarPackagingAndJarConfiguration.gradle

@@ -0,0 +1,11 @@
+plugins {
+	id 'war'
+	id 'org.springframework.boot' version '{version}'
+}
+
+bootBuildImage {
+	jar = bootWar.archiveFile
+}
+
+sourceCompatibility = '1.8'
+targetCompatibility = '1.8'

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/tasks/bundling/BootBuildImageIntegrationTests.gradle

@@ -3,5 +3,9 @@ plugins {
 	id 'org.springframework.boot' version '{version}'
 }
 
+if (project.hasProperty('applyWarPlugin')) {
+	apply plugin: 'war'
+}
+
 sourceCompatibility = '1.8'
 targetCompatibility = '1.8'